Technical Field
The present invention relates to flash memory, and in particular to methods for accessing data in a circular block mode and apparatuses using the same.
Description of the Related Art
Flash memory devices typically include NOR flash devices and NAND flash devices. NOR flash devices are random access—a host accessing a NOR flash device can provide the device any address on its address pins and immediately retrieve data stored in that address on the device's data pins. NAND flash devices, on the other hand, are not random access but serial access. It is not possible for NOR to access any random address in the way described above. Instead, the host has to write into the device a sequence of bytes which identifies both the type of command requested (e.g. read, write, erase, etc.) and the address to be used for that command. The address identifies a page (the smallest chunk of flash memory that can be written in a single operation) or a block (the smallest chunk of flash memory that can be erased in a single operation), and not a single byte or word. Since the NAND flash device operates in a block mode, a processing unit may program continuous data (that is, data of a series of LBA—logical block addresses) into a whole block. However, when partial data with specified LBA(s) of the block has been deleted and is then reprogrammed in replacement, it takes time for the processing unit to search for a new block of the NAND flash device and reprogram the other available data into the new block in advance. Accordingly, what is needed are methods for accessing data in a circular block mode and apparatuses that use these methods to address the aforementioned drawbacks.